In today's rapidly expanding wavelength division multiplexing optical network, a critical need exists for a simple, low cost, reconfigurable wavelength division multiplexer having an add/drop capability (often referred to simply as an “add/drop”). Add/drops find use in a network having a number of communication nodes where one or more wavelengths may require temporarily added and or dropped at a specific node. To achieve this adding and dropping, the optical fibers interconnecting the network must be remotely configurable to add and drop the wavelengths as required.
Currently, several different technologies are used to provide wavelength division multiplexing and the adding and dropping of individual wavelengths. The earliest wavelength division multiplexing technology used hardwired adds and drops. These adds and drops were permanent; they always added or dropped the same specific wavelengths at a given node. This had the drawback of not being remotely configurable.
The newer techniques for remotely configurable add and drop wavelength division multiplexing first demultiplex the individual wavelengths in the beam and then re-multiplex the individual wavelengths into a combined signal. One or more discrete switches are then inserted in the demultiplexed signal to add and drop wavelengths. This has the drawback of being complex and requiring redundant components.
What is needed in the art is a remotely reconfigurable add/drop. What is further needed in the art is a method of operating such add/drop to add and/or drop particular wavelengths of light on command.